Hrvatsko asfaltersko drutvo Croatian asphalt association
Raziliite tehonologije hladnog in-situ recikliranja u Europi i orgranienja uvjetovana
stanjima cesteVariety of cold-in-place recycling technologies
within Europe and limits regarding varyingroad conditions
Konrad Mollenhauer, Uni Kassel
Meunarodni seminar ASFALTNI KOLNICI 2017International seminar ASPHALT PAVEMENTS 2017
Opatija, 05. 06. 04. 2017.
Cold recycling mixtures vary considerable in
Europe
Binder types
Bitumen emulsion
Foamed bitumen
Cement
Binder contents
Mix design procedures
Laboratory Compaction methods
Accelerated Curing procedures
Mechanical test methods
Specification values
Project aim: Prepare harmonisation process
Cold Recycling Technologies in Europe: CoRePaSol-Project
Characterization of advanced cold
recycled bitumen stabilized
pavement solutions
Project funded by CEDR
2013-2014
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Cold Recycling-Technologies in Europe
Construction procedure
Variety of mix concepts
Effect of mix composition
Proposal for mix design
Limits regarding varying road conditions
Results of laboratory project
Recommendations
Content of presentation
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Cold Recycling: Mix and constrcution procedures
1. Milling / Granulation of existing
pavement
2. Mixing crushed pavement
material (in situ or in plant)
Bituminous binder (bitumenemulsion or foamed bitumen)
Cement (mineral binder oractive filler)
Additional aggregates toadjust grading
3. Paving
4. Compaction
5. Construction of surface layer(s)
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 4
Mixing and compaction at ambient temperatures require addition of water
Water results in high voids content and reduced bearing capacity after construction and
has to be removed from the layer:
Evaporation/Drainage in warm climate Addition of cement in moist climate
Cold recycled road materials: Variety of mixes
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 5
Collings et al., 2009
Cold recycled road materials: Variety of mixes
Type and degree of bonding
affects:
Visco-ealsticity / stiffness
Curing time
Cracking / rutting resistance
Water sensitivity
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1. Pre-assessment of mix granulate
Continuous grading (concrete type)
Assessment of optimum moisture content (mod. Proctor)
2. Selection of binder content range
BSM for dry climate or soft subground (only with foamed bitumen)
CBSM for moist climate
3. Compaction of specimens for mechanical tests
4. Laboratory curing
BSM: 3 days oven drying @ 50 C
CBSM: 28 days at room conditions
5. Specimen assessment
Void content (the lower the better)
Stiffness
Strength (e. g. Indirect tensile tests - ITS)
both properties: higher values are better however, not to be reached by excess addition of cement
CoRePaSol: Proposed (harmonised) mix design procedure
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 7
60 60
d0
d0
d60d60
Homogeneity of reclaimed asphalt is a
predominating property controlling the hot
recycling process
Nomograms for allowed RA contents are available
RA content results of homogeneity of RA properties and allowed tolerances within mix composition (binder content, grading, )
For cold recycling, effects of non-homogeneious
pavements are not known
Changing structural properties are obstancles for
Cold recycling (especially: cold-in-place)
Research question (within CoRePaSol-project):
What are the limits of homogeneities for cold recycling process?
What is the effect of (aged) bitumen in recycled asphalt within cold recycling mixtures?
Limits for varying pavement conditions for cold recycling
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Limits for varying pavement conditions for cold recycling
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Conditions of pavement to be
rehabilitated can vary
grown road with multiple maintenances during last centuries/decades
Road widening on one side
Small repair sections
Varying parameters:
Layers (materials)
Thickness
Conditions
In given milling horizon:
Asphalt layers
Hydraulically bound layers
Unbound layers
Transversal and longitudinal
differences
0
10
20
30
40
50
60
70
80
Pav
emen
t d
epth
[cm
]
SMA AC B AC T Cement Base Unbound Subbase
0
10
20
30
40
50
60
70
80
Pav
emen
t d
epth
[cm
]
BSM Unbound Subbase
Reclaimed asphalt 0/16
Binder content: 5.4 %,
TR&B: 63.5C,
Pen 23 1/10 mm
Reclaimed road concrete 0/22
Basaltic aggregates (to simulate reclaimed
unbound base)
Mix design (BCSM):
Addition of 3,6 % limestone filler to adjust grading
4 % added bitumen content
a) Foamed bitumen 50/70
b) Bitumen emulsion
2 % cement
Moisture content: 7,8 %
Laboratory study: Effect of mix granulate composition on cold recycled material
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0
10
20
30
40
50
60
70
80
90
100
0,0
62
5
0,1
25
0,2
5
0,5 1 2 4 8 16
32
pa
ssin
g [%
]sieve [mm]
Mix designReclaimed asphaltReclaimed road concrete
Selection of mix variations
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100 %
reclaimed
asphalt
Reclaimed
asphalt +
unbound base
Reclaimed
asphalt +
reclaimed road
concrete
Reclaimed
asphalt +
reclaimed road
concrete +
unbound base
Mix
variations
Reclaimed
asphalt
(RA)
Reclaimed
road
concrete
(RRC)
Unbound
material
(unb.)
A 100/0/0 96,4 - 3,6
B 75/0/25 77,1 22,9
C 50/25/25 48,2 25,0 26,8
D 50/0/50 48,2 - 51,8
E 40/20/40 38,6 20,0 41,4
F 0/50/50 - 50,0 50,0
G 0/25/75 25,0 75,0
H 0/0/100 - - 100,0
Laboratory study: Effect of mix granulate composition on cold recycled material
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0% 50% 100%
A 100/0/0
B 75/0/25
C 50/25/25
D 50/0/50
E 40/20/40
F 0/50/50
G 0/25/75
H 0/0/100
Mix granulate compositions
Reclaimed asphalt
Reclaimed road concrete
Unbound Aggregates
Cold recycling mix composition and test program
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Test program:
Static compaction (30 s 45.9 kN)
Specimen curing:
1 day in mould
2 days in mould (~ 20 C)
25 days at room conditions
Tests
Bulk density & void content
Indirect tensile strength (5 C)
Water sensitivity (ITS dry vs. 14 days in water)
CBRdry (California Bearing Ratio)
Mix preparation
Specimen curingITS CBR
Results: Void content after 28 days of (dry) curing at room conditions
Comparably high void contents
Low compaction energy (lowercompared to field compaction)
Coarse mix with low finescontent
Mixtures containing RA are
better to compact compared to
mixtures without RA
Little effect of reclaimed road
concrete vs. unbound
aggregates
Similar void content for
emulsion and foamed bitumen
mixtures
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0,0
5,0
10,0
15,0
20,0
25,0
30,0
A B C D E F G H
100%75% 50% 50% 40% - - -
- - 25% - 20% 50% 25% -
- 25% 25% 50% 40% 50% 75%100%
Vo
ids c
on
ten
t V
28
[%]
Bitumen emulsion
Foamed bitumen
Sample
RA
RRC
unb.
Results: Indirect tensile strength ITSdry after 28 days of curing (5 C)
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Foamed bitumen
Bitumen emulsion
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
1,6
A B C D E F G H
100%75% 50% 50% 40% - - -
- - 25% - 20% 50% 25% -
- 25% 25% 50% 40% 50% 75%100%
Ind
irect
ten
sile s
tren
gth
IT
Sd
ry(5C
) [M
Pa]
